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PROIZVODNJA MLEĈNE KISELINE NA DŢIBRI IZ PROIZVODNJE
BIOETANOLA

PRODUCTION OF LACTIC ACID ON STILLAGE FROM PRODUCTION OF

BIOETHANOL

Autor: Olga Pantid Učenica tredeg razreda Pete beogradske gimnazije Regionalni Centar za talente
Beograd II Mentor: Doktorant Dragana Mladenovid Tehnološko-metalurški fakultet Univerziteta u
Beogradu

REZIME

U proizvodnji bioetanola jedan od značajnijih problema je tretman otpada. U ovom radu je ispitivana mogućnost
korišćenja džibre iz proizvodnje bioetanola za proizvodnju mlečne kiseline i rast bakterija mlečne kiseline.
Korišćen je soj Lactobacillus rhamnosus ATCC 7469. Praćeni su parametri ovog procesa tj. koncentracija
mlečne kiseline, promena koncentracije šećera i promena biomase, u šaržnom postupku. Koncentraciju mlečne

kiseline je odreĎivana uz pomoć kiselinsko-bazne titracije. Promena koncentracije šećera je odreĎivana
spektofotometrijskom metodom sa 3,5-dinitrosalicinom kiselinom. Promenu broja živih ćelija je odreĎivan
metodom razblaženja i zasejavanja u Petri kutije sa MRS agarom. Ostvarena je koncentracija mlečne kiseline od
18.9 g/L, uz prinos 0.337 g/L, produktivnost 0.388 g/Lh, koeficijent prinosa 0.93 g/g. Postignute vrednosti su
slične vrednostima dobijenim u proizvodnji mlečne kiseline na kukuruznoj džibri bez podešavanja pH, a veće u
odnosu na vrednosti koje su dobijene na džibri titrikale. Uz ove rezultate ostvarena je značajna proizvodnja
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biomase, u periodu od 48 h biomasa je porasla sa 0.071 ×10 CFU/mL na 4.12×10 CFU/mL. Korišćeni soj je
probiotski i zbog ove osobine, ostatak koji nije iskorišćen u fermentaciji može se koristiti kao dodatak stočnoj
ishrani.

Kljuĉne reĉi: Mlečna kiselina, džibra, Lactobacillus rhamnosus, fermentacija, bioetanol

SUMMARY

In production of bioethanol one of the biggest issues is treatment of waste. This project investigates the
possibility of usage of stillage from the production of bioethanol, for producing lactic acid and as a base for
lactic acid bacteria growth. Lactobacillus rhamnosus ATCC 7469 was used and the following parameters were
monitored: concentration of produced lactic acid, the change of sugar concentration and bacterial mass in batch

process. The concentration of lactic acid was measured by acid-base titration. The change of sugar concentration
was measured by spectrophotometric method with 3.5-Dinitrosalicylic acid. Bacterial growth was followed
using a series of dilutions in 0.9% NaCl, grown in Petri dishes on MRS Agar. The following results were
achieved: lactic acid concentration of 18g/L, with a yeild of 0.337g/L, productivity of 0.388g/L and a high yield
coefficient 0.93g/g, which was very similair to the concentration of lactic acid produced in corn stilage
fermentation without pH value control, but higher than the yield obtained with the triticale stillage. In addition, a
significant production of bacterial mass in the 48h fermentation period was achieved, with bacterial growth
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increased two times in order of magnitude from 0.071 ×10 CFU/mL to 4.12×10 CFU/mL. Since L. rhamnosus
is a probiotic, the leftovers in the fermentation process can be used as an additive to livestock food.

Keywords: Lactic acid, stillage, Lactobacillus rhamnosus, fermentation, bioethanol

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